1. Field of the Invention
The invention relates to a light guide plate, more particularly to a light guide plate including a plurality of light-guiding structures.
2. Description of the Related Art
A conventional light guide plate utilizes total internal reflection to make light beams provided by a light source propagate from a first edge surface of the light guide plate to a second edge surface of the light guide plate opposite to the first edge surface. Since the light guide plate is provided for distributing the light beams to form a surface light source, where light beams exit the light guide plate from a light-exit surface, a bottom surface of the light guide plate opposite to the light-exit surface is normally etched with a plurality of light-reflecting dots such that light beams encountering these light-reflecting dots are diffused and reflected out through the light-exit surface.
The light-reflecting dots etched on the bottom surface of the abovementioned conventional light guide plate are capable of changing the direction of propagation of light beams so as to form the surface light source. However, distribution of the light-reflecting dots on the bottom surface and the sizes of the light-reflecting dots are not uniform such that the light beams are diffused unevenly, resulting in a relatively large loss of energy and poor light uniformity. Therefore, a bottom surface and a top surface of a modified conventional light guide plate are usually formed with V-shaped grooves arranged uniformly to reduce the loss of energy. An example of the modified conventional light guide plate is illustrated in FIG. 1 and FIG. 2. A light source 1 is disposed at a side of the modified conventional light guide plate, and is capable of providing light beams to the light guide plate. The modified conventional light guide plate includes a plate body 2 having a first surface formed with a plurality of first V-shaped grooves 3, each of which extends in a first direction. The plate body 2 further has a second surface opposite to the first surface and formed with a plurality of second V-shaped grooves 4, each of which extends in a second direction perpendicular to the first direction. For a 2-inch modified conventional light guide plate with a space of 0.1 mm between each adjacent pair of the first V-shaped grooves 3 and the second V-shaped grooves 4, there are approximately 300 first V-shaped grooves 3 and approximately 400 second V-shaped grooves 4.
Although the first and second V-shaped grooves 3, 4 are capable of diffusing the light beams such that the light beams exiting the modified conventional light guide plate have angles falling within a 30 degree range relative to a normal of the light guide plate, the following shortcomings are still present:
1. Since the first and second V-shaped grooves 3, 4 form elongated structures respectively on the first and second surfaces, minor adjustments on local areas where optical characteristics are relatively poor cannot be provided thereby. For instance, luminance of the light beams exiting the light guide plate is higher for regions of the modified conventional light guide plate proximate to the light source 1 than regions distal from the light source 1. However, the elongated structures formed by the first and second V-shaped grooves 3, 4 cannot provide further enhancement to the regions with poor luminance. Consequently, the luminance of light beams exiting the modified conventional light guide plate is not uniform.
2. The molds for forming the first and second V-shaped grooves 3, 4 require highly precise cutting finish. Since the structures formed by the first and second V-shaped grooves 3, 4 are elongated, the machining of the molds become more difficult, thereby increasing manufacturing cost.
3. Since the structures formed by the first and second V-shaped grooves 3, 4 are elongated, forming the light guide plate by injection molding can result in a high failure rate. In addition, the elongated structures are easily scratched during transport, thereby resulting in a high damage rate.